1. Field of the Invention
The subject invention relates to a work support apparatus. More specifically, the subject invention relates to a work support apparatus including a spring pin assembly for biasing a work piece against a stop.
2. Description of the Prior Art
In machining operations, it is necessary to position a work piece accurately at each station before performing work on it. Sometimes, this is accomplished by using a work support apparatus including a spring actuated locating pin assembly (spring pin assembly) to locate the work piece against a work stop by providing a lateral pressure between the work piece and the stop. Additionally, it is often necessary to retain the work piece at each station prior to introducing a primary means of securing the work piece. The spring pin assembly is required to act on a work piece in more than one axis to sufficiently retain the work piece. The combined reaction forces from the spring pin assembly and opposing stop sufficiently retain the work piece by applying force in multiple axis'.
The U.S. Pat. No. 4,793,603 to Wober et al. discloses a spring pin assembly that comprises a retaining pin partially enclosed in a cylindrical housing and insertable with the housing in a recess of a table. The cylindrical housing is press fit into the table. The housing is level or below a top surface of the table so that only an upper portion of the retaining pin is exposed above the top surface of the table. The retaining pin is provided with a flange that abuts the housing wall and is pressed against an inwardly angled rim of the housing by a compression spring disposed in the housing between the flange and a bottom portion of the housing. The flange of the retaining pin is provided with a curved side surface with which it abuts the housing wall. This curved side surface of the flange permits a deflection of the retaining pin and a simultaneous tilting of the flange, without the flange losing its guidance on the housing wall. The retaining pin is deflectable in every direction out of its normal position and is counter to the spring force. The spring force tends to press the retaining pin back into its normal upright position. Although the retaining pin may exhibit any desired shape, it has been found convenient if it is constructed as a cylindrical pin and provided with a rounded crest protruding out of the housing. Alternatively, the retaining pin may also be provided with a spherical or conical head if desired.
Spring pin assemblies, as described in U.S. Pat. No. 4,793,603 to Wober et. al. have been in use for many years. However, they do have some problems associated with their use. Most notably is that the spring pin assemblies of this type are press fit into the recess of the table. In order to remove the spring pin assembly from the table, it must be pressed out of the table from the opposing back side of the table. This often requires removing the table to gain access to the back side thereof. Often, once the spring pin assembly is removed, the housing looses the original press fit which often renders the spring pin assembly unusable. Another problem with the spring pin assemblies of this type is that the spring pin assemblies become contaminated with metal fines from the machining operation. When the locating pin pivots within the housing, an opening is created between the flange of the locating pin and the housing that allows the metal fines to enter. Over time, this accumulation of metal fines causes the spring actuated locating pin to fail. Yet another problem with the spring pin assemblies of this type is that the spring pin assembly does not provide for variation in sizes of the work piece other than that allowed by the locating pin range of motion.